In the continuous casting of steel bodies it is known to utilize curved continuous-casting molds (see the discussion at pages 707 ff. of The Making, Shaping and Treating of Steel, published by the United States Steel Company, Pittsburgh PA., ninth edition, copyright 1971).
Molds of this type, formed from plates, have been used in the curved continuous-casting process for the production of billets, blooms and other ingots of square, rectangular and generally polygonal profiles or cross-sections and impart a predetermined bend to the continuous ingot as it is cast and in the casting direction to avoid bending stresses in one relatively thin shell of hardened steel surrounding the soft inner core of the strand emerging from the mold.
In addition, it is desirable to impart to the channel a convergency in the direction of casting, i.e. a progressive reduction in the mold cross-section, corresponding to the shrinkage of the cooling cast strand to ensure continuous contact between the cooling strand and the inner wall of the mold over the entire length thereof. Furthermore, it is frequently desirable to so shape the corners on the mold or channel so that corner stresses on the cast body is minimized.
Because of wear, grooving and loss of conicity of the channel, the internal surfaces of the continuous casting mold must be periodically machined or refinished to restore the original surface finish and original dimensions of the mold channel.
With plate-formed molds, which have a complex geometry because of the aforedescribed criteria of bending and convergency, this machining is a serious problem because it is difficult to carry out and further because the material removal operation which refinishing involves leads to an increase in the mold cross-section and a corresponding increase in the cross-section of the continuous casting produced therein.
When it is desirable to retain the original dimensions of this cross-section, there have been only two alternatives heretofore. Either the wear is delayed so that refinishing or remachining is held in obeyance as long as possible, or one discards one or more mold plates or the entire mold.
To delay wear of the internal surfaces of the mold it is known to provide the internal surfaces with a coating of a wear resistant material such as zirconium oxide. However, these techniques are extremely expensive and have proved to be economically undesirable in many instances.
Thus one had to select either a complex and expensive machining process, generally with increase in the cross section of the mold channel and hence in the continuous casting produced therein, or a process whereby the internal surfaces of the mold were protected against wear to the greatest degree possible at extremely high cost, or a system whereby all or part of the mold was discarded when wear occured. None of these alternatives have proved to be fully satisfactory.